As a prior-art technique, a controller for an internal combustion engine, provided with an electric resistance type PM sensor is known as disclosed in Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2009-144577), for example. The prior-art PM sensor includes a pair of electrodes provided on an insulating material and is configured such that, when PM in the exhaust gas is captured between these electrodes, a resistance value between the electrodes is changed in accordance with the captured amount. As a result, in the prior-art technique, the PM amount in the exhaust gas is detected on the basis of the resistance value between the electrodes. Moreover, in the prior-art technique, a PM sensor is arranged downstream of a particulate filter that captures the PM in the exhaust gas and failure diagnosis of the particulate filter is made on the basis of a detected amount of the PM.
The applicant recognizes the following documents including the above-described document as relating to the present invention.